The price of oil price in the last few years has continued to rise. Even if the oil price falls partly in the interim, a high oil price must be assumed in the long term so that alternative methods for the production of fuel will become of greater interest in the future.
The best known method for the alternative production of fuel is the Fischer-Tropsch synthesis. The Fischer-Tropsch process is an industrial scale method for the conversion of synthesis gas (CO/H2) into liquid hydrocarbons. It is a synthesis reaction of CO/H2 mixtures on iron- or cobalt catalysts to form paraffins, alkenes and alcohols.
The chemical mechanism of the Fischer-Tropsch synthesis reaction (polymerisation) leads mainly to long-chain, only slightly branched (i.e. essentially linear) hydrocarbon molecules. Different chain lengths are found in the product mixture. The chain length range of C5-C20 is of particular interest for the production of fuels. The chain length can be adjusted by choice of catalyst (cobalt, iron, with promoters) and synthesis conditions (above all temperature, synthesis gas composition, pressure). The primary Fischer-Tropsch synthesis products are then processed chemically in the direction of higher fuel yields and qualities (e.g. hydrocracking, isomerisation, i.e. methods of crude oil processing).
Because of the characteristic feature of the chemical synthesis mechanism of forming mainly only slightly branched hydrocarbon molecules, the product is particularly suitable as a high-quality diesel fuel with a high cetane number and extremely low contents of sulphur and aromatics. Product mixtures with different hydrocarbon chain lengths can furthermore be specified with respect to vapour pressure, and/or distillation curves, inter alias by applying the highly developed crude oil refinery methods. These synthetically produced diesel fuels have the advantage of being particularly low-pollution and hence environmentally friendly.
At the moment, South Africa is the only country which covers a large part of its fuel requirements by means of the Fischer-Tropsch reaction. The synthesis gas for the synthesis is produced there from coal.
In Germany, the company Choren has developed a method for producing synthesis gas for the first time from biomass with the Carbo-V process and then fuel (so-called SunDiesel) with the help of the Fischer-Tropsch process. The Carbo-V® process is a three-stage gassing process with the partial processes:                low temperature gassing,        high temperature gassing and        endothermic flue flow gassing        
The biomass (water content 15-20%) is carbonised in the first process step continuously by partial oxidation (carbonising) with air or oxygen at temperatures between 400 and 500° C., i.e. broken down into tar-containing gas (volatile components) and solid carbon (biocoke).
In the second process step, the tar-containing gas is reoxidised in a combustion chamber above the ash-fusion point of the combustible materials substoichiometrically with air and/or oxygen to form a hot gasification medium.
In the third process step, the biocoke which is ground to form pulverised fuel is blown into the hot gasification medium. Pulverised fuel and gasification medium thereby react endothermally in the gasification reactor to form synthesis crude gas. This can be used then after corresponding conditioning as combustible gas for the production of current, steam and heat or as synthesis gas with the help of the Fischer-Tropsch process for the production of SunDiesel. Disadvantages of this process are that the gasification takes place in several steps and the biocoke must be ground up. In addition, this method is not suitable for gasification of wastes of all types.
It is hence an object of the present invention to provide a method which allows gasification of waste and also subsequent synthesis of fuels, as far as possible the entirety of the waste being able to be used.